Microsoft has sent out a “save the date” announcement for the first-ever Windows Phone Developer Summit, which is scheduled to take place in San Francisco on June 20 and 21.

The details surrounding the event venue are still shrouded in mystery—will it be held at the Moscone Center? Microsoft’s regional headquarters?—and the topics attendees will be learning about are even more secretive. There is, however, a decent chance that developers might get their first glimpse at Windows Phone 8 during this two-day summit.

In fact, we don’t even know who will be able to attend yet. A Microsoft representative has informed ZDNet’s Mary Jo Foley, however, that “You should expect a formal registration process as with most events. Will have more details in the coming weeks.” This seems to imply that the device will be at least somewhat open, rather than invite-only. But how much will attendance cost?